Sorption of hexavalent chromium ion onto natural swelling clay and acidified clay as a nano adsorbent: Kinetic and thermodynamic study

Q1 Environmental Science

Environmental Nanotechnology, Monitoring and Management Pub Date : 2025-09-05 DOI:10.1016/j.enmm.2025.101098

Niraka Blaise , Aguiza Abai Emmanuel , Mohamed Oubaouz , El Mostafa Erradi , Cherrat Ayoub , Kofa Guillaume Patrice , Ndi Koungou Sylvère , Hambate Gomdje Valery , Abdelilah Chtaini

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Abstract

Natural clay (NC) from Makabaye (Far North Cameroon) was pre-treated according to the stocks method and the resulting powder was subjected to acid treatment (HCl at 0.5 M) to obtain acidified clay (AC) material. These materials (NC and AC) were subjected to morphological and structural characterization and then to successive adsorption (in batch mode) and desorption studies for hexavalent chromium until AC lost its adsorptive properties. These analyses showed the exfoliation of the clay after acidification. The influence of experimental parameters such as the variation in contact time, the mass of adsorbent, the pH of the solutions, the initial concentration of Cr (VI) ions were studied showed that each of the parameters influences the adsorption process. The results showed that adsorption equilibrium was reached after 20 min with both adsorbents. The optimum quantities of Cr (VI) ions adsorbed by the adsorbent were obtained for masses of 0.100 g. Maximum adsorption of Cr (VI) ions was obtained at pH = 3 with both adsorbents. This work also showed that by keeping the optimum parameters fixed, the quantity of chromium ions adsorbed increased significantly before stabilising at 15 mg/L with the two clay samples. Under these same optimum conditions, the maximum quantity adsorbed was obtained with the acidified clay and the natural clay, i.e. 29.41 mg/g and 27.78 mg/g respectively. The application of adsorption isotherms has shown that the Langmuir model (R² = 0.980 with AC and R² = 0.971 with NC) and Dubinin-Radushkevich model (R² = 0.917 with AC and R² = 0.991 with NC) better describes the adsorption mechanism of Cr (VI) ions than those of Freundlich and Temkin model. The kinetic study has shown that the pseudo-second order equation satisfactorily describes the adsorption mechanism (R² = 0.998 with AC and R² = 0.995 with NC). The thermodynamic study showed that the adsorption of Cr (VI) on the two adsorbents is spontaneous, exothermic with NC and endothermic with AC. The desorption study showed that the adsorbent (AC) could be regenerated to 98.32 % after 70 min under agitation at 150 rpm for a concentration of 1.5 M EDTA. The reused adsorbent showed desorption percentages ranging from 98.88 % (after the 1st recycling) to 85.56 % (after the 6th recycling). A very rapid decrease in the desorption of chromium by AC was observed from the 7th cycle of reuse (57.68 %) until the complete loss of this desorption at the 10th cycle (0.12 %).

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六价铬离子在天然膨胀粘土和酸化粘土上的纳米吸附：动力学和热力学研究

根据原料法对来自Makabaye（远北喀麦隆）的天然粘土（NC）进行预处理，并对所得粉末进行酸处理（0.5 M的HCl）以获得酸化粘土（AC）材料。这些材料（NC和AC）进行了形态和结构表征，然后进行了六价铬的连续吸附（批处理模式）和解吸研究，直到AC失去其吸附性能。这些分析显示了酸化后粘土的剥落。研究了接触时间、吸附剂质量、溶液pH、Cr （VI）离子初始浓度等实验参数对吸附过程的影响。结果表明，两种吸附剂在20 min后均达到吸附平衡。在质量为0.100 g时，吸附剂吸附Cr （VI）离子的最佳量。两种吸附剂在pH = 3时对Cr （VI）离子的吸附量最大。这项工作还表明，在保持最佳参数不变的情况下，两种粘土样品的铬离子吸附量在稳定在15 mg/L之前显著增加。在相同的最佳条件下，酸化粘土和天然粘土的吸附量最大，分别为29.41 mg/g和27.78 mg/g。吸附等温线的应用表明，Langmuir模型（AC时R2 = 0.980， NC时R2 = 0.971）和Dubinin-Radushkevich模型（AC时R2 = 0.917， NC时R2 = 0.991）比Freundlich和Temkin模型更能描述Cr （VI）离子的吸附机理。动力学研究表明，拟二级吸附方程较好地描述了吸附机理（AC = 0.998, NC = 0.995）。热力学研究表明，两种吸附剂对Cr （VI）的吸附均为自发吸附，NC为放热吸附，AC为吸热吸附。解吸研究表明，在1.5 M EDTA浓度下，150 rpm搅拌70 min后，吸附剂（AC）的再生率可达98.32%。重复使用吸附剂的解吸率为98.88%（第一次回收）~ 85.56%（第6次回收）。从第7次循环使用开始，活性炭对铬的解吸率迅速下降（57.68%），直到第10次循环完全失去这种解吸率（0.12%）。

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来源期刊

Environmental Nanotechnology, Monitoring and Management Environmental Science-Water Science and Technology

CiteScore

13.00

自引率

0.00%

发文量

132

审稿时长

48 days

期刊介绍： Environmental Nanotechnology, Monitoring and Management is a journal devoted to the publication of peer reviewed original research on environmental nanotechnologies, monitoring studies and management for water, soil , waste and human health samples. Critical review articles, short communications and scientific policy briefs are also welcome. The journal will include all environmental matrices except air. Nanomaterials were suggested as efficient cost-effective and environmental friendly alternative to existing treatment materials, from the standpoints of both resource conservation and environmental remediation. The journal aims to receive papers in the field of nanotechnology covering; Developments of new nanosorbents for: •Groundwater, drinking water and wastewater treatment •Remediation of contaminated sites •Assessment of novel nanotechnologies including sustainability and life cycle implications Monitoring and Management papers should cover the fields of: •Novel analytical methods applied to environmental and health samples •Fate and transport of pollutants in the environment •Case studies covering environmental monitoring and public health •Water and soil prevention and legislation •Industrial and hazardous waste- legislation, characterisation, management practices, minimization, treatment and disposal •Environmental management and remediation